diff --git a/gitmirror/src/git.rs b/gitmirror/src/git.rs
index c668e1940..74135c1c9 100644
--- a/gitmirror/src/git.rs
+++ b/gitmirror/src/git.rs
@@ -16,8 +16,9 @@ pub(crate) struct TempRepository {
 }
 
 impl TempRepository {
-    fn new(repo: gix::Repository, dir: TempDir) -> Self {
-        Self { repo, _dir: dir }
+    pub fn open(dir: TempDir) -> Result<Self, gix::open::Error> {
+        let repo = gix::open(dir.path())?.with_object_memory();
+        Ok(Self { repo, _dir: dir })
     }
 }
 
@@ -72,10 +73,7 @@ pub(crate) fn open_scratch(
         .join("\n");
     std::fs::write(info_dir.join("alternates"), format!("{alternates}\n")).map_err(internal)?;
 
-    let repo = gix::open(scratch.path())
-        .map_err(|e| XrpcError::Internal(e.to_string()))?
-        .with_object_memory();
-    Ok(TempRepository::new(repo, scratch))
+    TempRepository::open(scratch).map_err(|e| XrpcError::Internal(e.to_string()))
 }
 
 pub(crate) fn commit_log_walk<'repo>(
@@ -125,8 +123,7 @@ mod tests {
     fn temp_repository_removes_scratch_dir_on_drop() {
         let dir = tempfile::tempdir().unwrap();
         gix::init_bare(dir.path()).unwrap();
-        let repo = gix::open(dir.path()).unwrap().with_object_memory();
-        let temp = TempRepository::new(repo, dir);
+        let temp = TempRepository::open(dir).unwrap();
         let path = temp.git_dir().to_path_buf();
         assert!(path.exists());
         // Derefs to gix::Repository.
diff --git a/gitmirror/src/layout.rs b/gitmirror/src/layout.rs
new file mode 100644
index 000000000..d0a097a1d
--- /dev/null
+++ b/gitmirror/src/layout.rs
@@ -0,0 +1,58 @@
+use std::path::PathBuf;
+
+use jacquard_common::types::did::Did;
+use tracing::error;
+
+use crate::git::TempRepository;
+
+#[derive(Debug, Clone)]
+pub(crate) struct Layout {
+    scan_path: PathBuf,
+}
+
+impl Layout {
+    pub fn new(scan_path: PathBuf) -> Self {
+        Self { scan_path }
+    }
+
+    pub fn repo_path(&self, repo: &Did) -> PathBuf {
+        self.scan_path.join(repo.to_lowercase().as_str())
+    }
+
+    pub fn open_scratch(&self, dids: &[&Did]) -> anyhow::Result<Option<TempRepository>> {
+        let mut seen: Vec<&Did> = Vec::new();
+        let mut object_dirs = Vec::new();
+        for &did in dids {
+            if seen.contains(&did) {
+                continue;
+            }
+            seen.push(did);
+            let object_dir = match std::fs::canonicalize(self.repo_path(did).join("objects")) {
+                Ok(path) => path,
+                Err(err) => {
+                    error!(error = %err, "repo not found");
+                    return Ok(None);
+                },
+            };
+            object_dirs.push(object_dir);
+        }
+        if object_dirs.is_empty() {
+            return Err(anyhow::anyhow!(
+                "open_scratch requires at least one repo".to_owned(),
+            ));
+        }
+        let scratch = tempfile::tempdir()?;
+        gix::init_bare(scratch.path())?;
+
+        let info_dir = scratch.path().join("objects").join("info");
+        std::fs::create_dir_all(&info_dir)?;
+        let alternates = object_dirs
+            .iter()
+            .map(|p| p.display().to_string())
+            .collect::<Vec<_>>()
+            .join("\n");
+        std::fs::write(info_dir.join("alternates"), format!("{alternates}\n"))?;
+
+        Ok(Some(TempRepository::open(scratch)?))
+    }
+}
diff --git a/gitmirror/src/main.rs b/gitmirror/src/main.rs
index f57f9d9b3..ef22364ff 100644
--- a/gitmirror/src/main.rs
+++ b/gitmirror/src/main.rs
@@ -5,6 +5,7 @@ use clap::{Parser, Subcommand};
 
 mod diff;
 mod git;
+mod layout;
 mod merge;
 mod xrpc;